Well, certain principles never really become tedious (to me). If we are working on controlling our center or being more circular or a principle like that then its not so redundant because almost every technique can be tied into those principles.

But say for instance we are working on only Kokyu nage (or different variations of it) for an entire class... that can be boring. For one... kokyu nage isnt really that exciting of a technique in the first place .. all u do is turn and throw. And doing an already boring technique for an entire class, can definitely make it worse.

However, its very rare that we do stuff like this... and its also very rare that i find myself bored during aikido. Just every now and then. And who knows maybe its not the techniques maybe its just my mood at the time...